Snap switch



Patented Dec. 8, 1942 2.304.400 SNAP SWITCH Malcolm W. Eaton,

poration of Illinois Freeport, lll., signor to Micro Switch Corporation,Freeport,

Ill., a cor- Application August 3, 1940, Serial No. 350,733 3 Claims.(Cl. 200-67) 'l'he present invention relates to snap acting electricswitches.

My invention constitutes an improvement upon the snap switch of U. S.Patent 1,960,020 to P. K. McGall, May 22, 1934.

'I'he McGall snap switch is of the self returning type. Thus, althoughits snap acting spring has two stable positions between which it snapsit is capable of lying normally in only one of those positions. When anactuating force is applied to the switch, the snap spring snaps out ofits normal position into its other position, but returns K automaticalyto its flrst or normal position when f the actuating force is released.The McGau switch possesses a desirable combination of operatingprecision, large control capacity, and small operating eort, which haswon4 its adoption in a large number of electrical control applications.However, in many of these applications it has been desirable that theswitch should not exhibit a. self returning action but rather afteractuation in one direction should require a second distinct actuationfor effecting its return operation. Furthermore, it is desirable thatthe switch, although requiring separate actuations for operation in twodirections, should nevertheless retain its original precision,sensitivity and high control capacity.

It is an object of the present invention to provide a switch of theMcGall type without a selfreturning action, but yet with the fullprecision, sensitivity and control capacity of the McGall switch.Another object is the provision of means for effecting a returnactuation of such a. switch with a snap action for utilizing itsinherent precision, sensitivity and high control' capacity in so doing.These and other objects and advantages will become apparent in thefollowing description of a specific embodiment of my invention whichserves by way of example to illustrate the manner in which the inventionmay be carried into practice. However. the inventionis not to be limitedto the particular details of any embodiment or example. In the drawing:`

Fig. 1 is a longitudinal section of a complete snap switch embodying mypresent invention;

Fig. 2 is a partial plan view of the internal construction of the switchin Fig. l, constituting a section along the line 2-2 of Fig. 1; and

Fig. 3 is an exploded pictorial view showing certain of the parts of theswitch of Fig. 1 and their orientations with respect to each other.

As shown in Fig. 1 the switch Iincludes an insulating'housing I0, and aninsulating cover I2 bushings of different lengths located along side ofeach other and embedded in the bottom of the insulating housing I0 (ofwhich only bushing I8 appears in the sectional view of Fig. l) supportstationary contacts I8 and 20.y The details of this particular part ofthe switch construction are shown in U. S. Patent 2,172,673 issuedSeptember 12,1939 to M. W. Eaton.V

At the other end of the housing, a threaded metal bushing 22 embedded inthe bottom of the housing I0 supports a spacer 24 and a spring anchor26. A single screw, 28 mounts the parts 24 and 26 and clamps also the end of a tension member 30 of a toggle spring 36. As best shown in Fig. 3this toggle spring is cut and formed from a single piece of thin leafspring material and includes the central tension member 30 and twocompression side members 32 connected together at the movable end 34 ofthe toggle, which end supports electric contact 38. As is shown in Fig.l the side legs 32 are bowed in compression in the assembled switch. Theends of these side legs or thin leaf compression springs 32 arepivotally supported in notches 40 inv the'ends of the legs 42 or theU-shaped spring anchor 26.

-The tension member 30 of the toggle spring, being fastened under thescrew 28 at the center of the base of the U-shaped anchor 26, vextendsout over the'space between the legs 42 of that anchor, where it may bedeflected up and down for causing the toggle spring 36 to snap back andforth between the two stationary contacts I8 and 20. The portion oftension spring 30 that lies over this space between the /two legs 42 ofthe spring anchor constitutes a sensitive 'area of the spring which maybe moved through a slight distance to cause a much larger snap motion ofthe movable end 34 carrying the contact 38. A rigid actuating plunger 44is supported by the cover I2 and arranged to slide up and down thereinin alignment with the sensitive area of tension spring 30. Accordingly,an actuating force may be applied to this rigid plunger 44 to move thesensitive larea down a slight distance for causing the movable end 34 ofthe toggle 38 to snap down, carrying movable contact 38 down intoengagement with stationary contact I8. The operation of the switch inresponse to actuation by the plunger 44 is sensitive and precise andinduces a for said housing. Two separate threaded metal good snap actionto provide high load handling capacity for the-switch. In snapping downto carry contact 38 from its upper position in engagement with upperstationary contact 20 down to its lower position in engagement withlower stationary contact I8, the toggle moves a sumcient distance that'it goes "over center and so tends to remain in its new position.

A formed spring strip or lever` 46 has an arch 48, positioned in thespace between thelegs of the U-shaped spacer 24 and spring anchor 26with the peak of its arch lying just under the sensitive area of thetension spring 3D. One end 50 of this spring fulcrums in the curve ofthe U of this spacer and spring anchor. The other end 52 is forked tofit a circumferential notch 54 in, actuating plunger 58 that slides upand down in a hole in the bottom of the housing I 0. The

plunger 56v may be moved upward to raise the peak of the arch I8 againstthe bottoxn surface of tension spring 30 at its sensitive area for inturn causing the toggle spring 36 to snap back to its upper position.The spring 46 is resilient first to limit the forces that may betransmitted by it to the spring 30 for limiting the stresses in thespring 30, and second to insure that actuation of the plunger S cannotinterfere with, nor supersede, the control of the switch Vexercised bythe rigid actuating plunger 44. This feature is particularlyadvantageous when the switch is employed as a safety limit. For such usethe controlled apparatus actuates the rigid plunger 44 to effect thesafety or limit stop and the plunger 56 serves as the reset forrestoring the controlled apparatus to operation.

The present invention provides a new and improved construction foradapting the McGall type ofswitch with its inherent precision,sensitivity and high control capacity for non-selfsustained, or doubleactuation, and thereby gives the switch a separate reset action of highprecision and sensitivity with the full control capacity of the switch.

It will be apparent to those skilled in the art that the invention iscapable of numerous modications and variations within the scope of thefollowing claims.

I claim:

l. In a device of the class described, the com.- bination with a switchhousing having a cavity therein and a ledge at one end of said cavity, aU-shaped support on this ledge with the legs of the U extending towardthe center of the housing, a snap-spring mounted on said U- shapedsupport, said spring having a sensitive area spaced slightly above thesurface of the` ledge in the space between the legs of the U, and.

actuating means for pressing down on said sensitive area for actuatingsaid spring, of, an arched lever extending into the shallow spacebetween said ledge and snap spring, having one end fulcrumed on thesurface of the ledge in the curve of the U, and having the peak of thearch under said sensitive area of the spring,` and means for lifting theother end of the lever to lift said peak against said sensitive area foractuating said snap-spring.

2. The combination with an elongated switch housing having a well and aledge-like supporting surface alongside thereof, and a thin .leaf snapspring having a sensitive area adapted to be pressed for snapping saidspring, of, means for supporting said spring over said supportingsurface and over said well, with said sensitive area spaced slightlyabove said supporting surface, an arched, resilient,` thin-leaf lever,extending into the shallow space between said spring and supportingsurface, said lever having one end resting on said surface to provide afulcrum, having the peak of said arch under said sensitive area, andhaving its other end in said well, and a movable actuating member insaid well for lifting said other end of said arched lever for in turncausing said lever to press up against the sensitive area of saidspring.

3. In combination in a device of the class described, a supportingsurface, a thin-leaf snapspring having a sensitive area such that asmall motion of said sensitive area causes a snap motion of said spring,means for supporting said spring abovesaid surface with said sensitivearea spaced slightly therefrom, a thin-leaf lever extending into theshallow space between said spring and said supporting surface for pryingup against the lower face of said sensitive area of the spring, firstactuating means 4for actuating said lever to pry up against said lowerface of said sensitive area for causing a snap action of said spring,and second actuating means, independent of both said lever and saidfirst actuating means, for applying an actuating force down against thetop face of said sensitive area of said spring for causing a snap motionof said spring.

MALCOLM W. EATON.

